| 1. |
- Abeywickrama, Nilanga, 1976, et al.
(författare)
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Computation of Parameters of Power Transformer Windings for Use in Frequency Response Analysis
- 2007
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Ingår i: IEEE Transactions on Magnetics. - 0018-9464. ; 43:5, s. 1983-1990
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Tidskriftsartikel (refereegranskat)abstract
- We present a 3-D model for calculating magnetic fields in a power transformer and the effective parameters (inductance and resistance)of its windings. The transformer is representative of large transformers with power ratings ranging from hundreds of kilovolt amperes to hundreds of megavolt amperes. The model accounts for anisotropic frequency-dependent properties of the laminated transformercore and eddy currents in the steel sheets. We discuss the results of the calculations performed in the frequency range 10 Hz–10 MHz, and show that the largest variations of both the magnetic field and parameters of the windings take place at frequencies below 10 kHz and, at frequencies higher than 1 MHz, the magnetic core does not significantly affect the variation of the effective parameters.
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| 2. |
- Abeywickrama, Nilanga, 1976, et al.
(författare)
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Infuence of Core Characteristics on Inductance Calculations for Modeling of Power Transformers
- 2006
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Ingår i: Industrial and Information Systems, 2006. ICIIS 2006. International Conference. ; , s. 24-29
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Konferensbidrag (refereegranskat)abstract
- Calculations of effective parameters (inductance and resistance) of transformer windings, including core characteristics, are presented in this paper. Both anisotropic nature of the core and eddy currents in the electrical steel sheets are accounted for. A 3D model is developed and used to find out the inductance and resistance of transformer windings in the frequency range from 10 Hz to 10 MHz. It is shown that strongest variations of the magnetic field inside the core and of the effective parameters occur below ~ 10 kHz, whereas the effect of the magnetic core is negligible above 1 MHz.
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| 3. |
- Podoltsev, Alexander, 1951, et al.
(författare)
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Multi-scale computations of parameters of transformer windings at high frequencies. Part I
- 2007
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Ingår i: IEEE Transactions on Magnetics. - 0018-9464. ; 43:11, s. 3991 - 3998
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Tidskriftsartikel (refereegranskat)abstract
- A hierarchical multi-scale approach to modeling of high frequency phenomena in power transformers is proposed. The method is based on considering high frequency effects on two spatial levels. Part I of the paper focuses on a small-scale level where eddy current as well as geometrical and proximity effects in conductors of transformer windings are examined. The developed computer model accounts for anisotropic frequency-dependent effective diamagnetic properties of transformer windings, which are represented as composite media with periodic structure. Effective characteristics of the laminated transformer core are calculated taking into account anisotropic magnetic properties of steel sheets. The obtained frequency-dependent parameters of transformer elements are further used in Part II for computing effective inductances and resistances of windings and integral losses on a large-scale level, i.e. for the whole transformer.
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| 4. |
- Podoltsev, Alexander, 1951, et al.
(författare)
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Multi-scale computations of parameters of transformer windings at high frequencies. Part II
- 2007
-
Ingår i: IEEE Transactions on Magnetics. - 0018-9464. ; 43:12, s. 4076 - 4082
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Tidskriftsartikel (refereegranskat)abstract
- This part of the paper focuses on implementation of hierarchical multi-scale approach for modeling high frequency electromagnetic processes in power transformers. A large-scale 3D computer model for calculating magnetic fields in a transformer and evaluating effective parameters (inductance and resistance) of its windings and losses is presented. The model accounts for complex, anisotropic and frequency-dependent effective diamagnetic properties of the windings, which were obtained by solving small-scale 2D field problems as described in Part I of this paper. Results of the computations performed for a test transformer are analyzed in the frequency range 10 Hz – 10 MHz. Effects of windings conditions (open and short-circuited) and their location on the transformer core are discussed.
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| 5. |
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| 6. |
- Serdyuk, Yuriy, 1963, et al.
(författare)
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Dielectric Properties of Composite Structures: 3D Simulations versus Experiments
- 2002
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Ingår i: IEEE Annual Report Conference on Electrical Insulation and Dielectric Phenomena. - 0780375025 ; , s. 142-145
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Konferensbidrag (refereegranskat)abstract
- Results of numerical simulations of the dielectric properties of binary composites with three-dimensional structures are verified by means of comparison with experimentally obtained data. Two different heterogeneous structures - regular (periodic) and stochastic, were studied. Frequency dependencies of the complex dielectric permittivities of the materials of the constituent phases of the composites were measured and were used as input for computer modelling together with their known geometrical parameters. Calculations were based on the effective media approach, and the associated field problem was solved numerically using the finite-volume method and the finite-element method. The results of the measurements and the computations of the effective complex permittivities of the composite materials are compared and are analysed.
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| 7. |
- Serdyuk, Yuriy, 1963, et al.
(författare)
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Numerical calculation of electric fields, losses and interfacial charge densities in water-treed dielectric composite structure
- 2004
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Ingår i: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 61:3-4, s. 171-187
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Tidskriftsartikel (refereegranskat)abstract
- Results of the computer modeling and an analysis of electrical processes in a water-treed polyethylene (XLPE) are presented. The water-treed region is considered as a binary composite structure in frequency domain. Electric fields, energy losses and interfacial charge densities are calculated and are examined using a simplified layered model and 3D model of a real water-treed XLPE insulation. It is shown that the interfacial charges in the bulk of the composite structure build up mostly due to differences in conductive properties of the constituent phases, and the distributions of the electric fields and losses are determined also by the morphology of the water-treed region.
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| 8. |
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| 9. |
- Serdyuk, Yuriy, 1963, et al.
(författare)
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Numerical simulations of dielectric properties of composite material with periodic structure
- 2005
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Ingår i: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 63:11, s. 1073-1091
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Tidskriftsartikel (refereegranskat)abstract
- Results of computer simulations and measurements of frequency-dependent dielectric properties of a binary composite material are presented. The studied composite had well-defined 3D periodic structure and was made of paraffin and paper laminate. In the considered frequency range (10(-3) 10(3) Hz), both the constituents were characterized by significantly different dispersive properties of complex dielectric permittivities. These frequency-dependent parameters were measured and were used for 3D numerical simulations of the effective dielectric properties of the mixture. The simulations were performed using two methods, the finite-volume method and the finite-element method. Frequency variations of the computed effective complex permittivity of the composite are discussed and are compared with the experimental data. The results of the simulations show that the distributions of the micro-scale electric field and dielectric losses in the volume of the composite material are strongly frequency dependent. This effect is also analyzed using classical models for composite dielectric structures.
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